The present invention relates to an apparatus for filtering and separating flowing medium by reverse osmosis, ultrafiltration and microfiltration, and has a membrane or element stack that is disposed in a closed housing and is formed of disk-shaped spacers as well as filter elements, whereby a respective filter element is disposed between each two spacers, about which the flowing medium flows.
An apparatus of this general type is known (see applicants' U.S. Pat. No. 4,892,657). With this known apparatus, the housing is in the form of an essentially cylindrical tube, with the element stack being accommodated in a hollow space of the tube that is closed off at both ends by end members or flanges that are sealed relative to the inner wall of the tube. When dealing, for example, with flowing medium or unprocessed solution in the form of a no salt content water, but also, for example, with radioactively contaminated water, apparatus of this type must operate at very high pressures, for example in the range of from 10 to 15 bar. If the known apparatus having a tubular housing were to be operated at such pressures, the tube wall would have to be extremely thick to prevent the apparatus from bursting at pressures at which such processes are designed to be carried out. Additional stability enhancing measures might also have to be undertaken in the region of the end flanges or members in order to be able to confront these pressures. All of this results in considerable drawbacks, because taking such measures to make the apparatus pressure resistant makes the apparatus very expensive to produce, while at the same time considerably increasing the weight thereof, as a consequence of which the apparatus can no longer be used for a number of otherwise possible applications where the price-to-output ratio has now become too negative.
Apparatus of this type should be usable, for example, in great numbers on location, i.e. directly at the source of the contaminated flowing medium, and must in this connection also be easy to handle, yet must nonetheless be able to readily withstand high operating pressures.
It is therefore an object of the present invention to provide an apparatus for filtering and separating flowing medium of the aforementioned general type that has the ability to withstand high operating pressures in the range of 15 bar and greater, even during prolonged periods of use, that is also suitable for large quantity use due to its low manufacturing cost, that can also be used in very small plants where little space is available, and that is also suitable for recovering drinking water for human consumption and to meet hygiene requirements in the food industry.